Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is
none, oncePerWeek, severalPerWeek
or daily.
Build a proper factor for the responses below and store it in a variable
w.
Print the factor.
Write the code to count the numbers of occurrences of each level and
print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 × 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the
results.
Next, understand why an error is generated and use replace
argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor
w from it.
Finally, count the numbers of occurrences of each level in
w.
Ensure, that levels are in order provided in the variable
lvs.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "daily" "none" "severalPerWeek"
sample( lvs, 3 )
[1] "none" "daily" "oncePerWeek"
sample( lvs, 3 )
[1] "severalPerWeek" "none" "daily"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] none oncePerWeek daily daily daily oncePerWeek oncePerWeek none oncePerWeek none
[11] severalPerWeek daily severalPerWeek oncePerWeek none oncePerWeek daily oncePerWeek daily severalPerWeek
[21] oncePerWeek daily severalPerWeek none daily severalPerWeek daily daily daily none
[31] oncePerWeek none oncePerWeek none severalPerWeek oncePerWeek none severalPerWeek none daily
[41] severalPerWeek none severalPerWeek severalPerWeek daily daily severalPerWeek severalPerWeek oncePerWeek severalPerWeek
[51] severalPerWeek oncePerWeek severalPerWeek daily none oncePerWeek none daily daily daily
[61] oncePerWeek oncePerWeek oncePerWeek none none severalPerWeek daily none daily daily
[71] severalPerWeek severalPerWeek daily none oncePerWeek daily none daily oncePerWeek none
[81] severalPerWeek none none daily severalPerWeek oncePerWeek severalPerWeek daily oncePerWeek none
[91] oncePerWeek oncePerWeek oncePerWeek severalPerWeek daily none oncePerWeek none oncePerWeek severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 × 2
f n
<fct> <int>
1 none 24
2 oncePerWeek 26
3 severalPerWeek 23
4 daily 27
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its
levels.
The factor w from the previous exercise will be then shown
in this order: none, oncePerWeek,
severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed:
daily, severalPerWeek,
oncePerWeek, none.
Apply to w one of the fct_ functions from the
tidyverse library to produce a factor w2 with
the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and
compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 × 2
f n
<fct> <int>
1 daily 27
2 severalPerWeek 23
3 oncePerWeek 26
4 none 24